Inhibitors of farnesyl-protein transferase

ABSTRACT

The present invention is directed to compounds which inhibit farnesyl-protein transferase (FTase) and the farnesylation of the oncogene protein Ras. The invention is further directed to chemotherapeutic compositions containing the compounds of this invention and methods for inhibiting farnesyl-protein transferase and the farnesylation of the oncogene protein Ras.

BACKGROUND OF THE INVENTION

The Ras gene is found activated in many human cancers, including colorectal carcinoma, exocrine pancreatic carcinoma, and myeloid leukemias. Biological and biochemical studies of Ras action indicate that Ras functions like a G-regulatory protein, since Ras must be localized in the plasma membrane and must bind with GTP in order to transform cells (Gibbs, J. et al., Microbiol. Rev. 53: 171-286 (1989). Forms of Ras in cancer cells have mutations that distinguish the protein from Ras in normal cells.

At least 3 post-translational modifications are involved with Ras membrane localization, and all 3 modifications occur at the C-terminus of Ras. The Ras C-terminus contains a sequence motif termed a "CAAX" or "Cys-Aaa¹ -Aaa² -Xaa" box (Aaa is an aliphatic amino acid, the Xaa is any amino acid) (Willumsen et al., Nature 310: 583-586 (1984)). Other proteins having this motif include the Ras-related GTP-binding proteins such as Rho, fungal mating factors, the nuclear lamins, and the gamma subunit of transducin.

Farnesylation of Ras by the isoprenoid farnesyl pyrophosphate (FPP) occurs in vivo on Cys to form a thioether linkage (Hancock et al., Cell 57:1167 (1989); Casey et al., Proc. Natl. Acad. Sci. USA 86:8323 (1989)). In addition, Ha-Ras and N-Ras are palmitoylated via formation of a thioester on a Cys residue near a C-terminal Cys farnesyl acceptor (Gutierrez et al., EMBO J. 8:1093-1098 (1989); Hancock et al., Cell 57: 1167-1177 (1989)). Ki-Ras lacks the palmitate acceptor Cys. The last 3 amino acids at the Ras C-terminal end are removed proteolytically, and methyl esterification occurs at the new C-terminus (Hancock et al., ibid). Fungal mating factor and mammalian nuclear lamins undergo identical modification steps (Anderegg et al., J. Biol. Chem. 263: 18236 (1988); Farnsworth et al., J. Biol. Chem. 264: 20422 (1989)).

Inhibition of Ras farnesylation in vivo has been demonstrated with lovastatin (Merck & Co., Rahway, N.J.) and compactin (Hancock et al., ibid; Casey et al., ibid; Schafer et al., Science 245:379 (1989)). These drugs inhibit HMG-CoA reductase, the rate limiting enzyme for the production of polyisoprenoids and the farnesyl pyrophosphate precursor. It has been shown that a farnesyl-protein transferase using farnesyl pyrophosphate as a precursor is responsible for Ras farnesylation. (Reiss et al., Cell, 62: 81-88 (1990); Schaber et al., J. Biol. Chem., 265: 14701-14704 (1990); Schafer et al., Science, 249: 1133-1139 (1990); Manne et al., Proc. Natl. Acad. Sci USA, 87: 7541-7545 (1990)).

Inhibition of farnesyl-protein transferase and, thereby, of farnesylation of the Ras protein, blocks the ability of Ras to transform normal cells to cancer cells. The compounds of the invention inhibit Ras farnesylation and, thereby, generate soluble Ras which, as indicated infra, can act as a dominant negative inhibitor of Ras function. While soluble Ras in cancer cells can become a dominant negative inhibitor, soluble Ras in normal cells would not be an inhibitor.

A cytosol-localized (no Cys-Aaa¹ -Aaa² -Xaa box membrane domain present) and activated (impaired GTPase activity, staying bound to GTP) form of Ras acts as a dominant negative Ras inhibitor of membrane-bound Ras function (Gibbs et al., Proc. Natl. Acad. Sci. USA 86: 6630-6634 (1989)). Cytosollocalized forms of Ras with normal GTPase activity do not act as inhibitors. Gibbs et al., ibid, showed this effect in Zenopus oocytes and in mammalian cells.

Administration of compounds of the invention to block Ras farnesylation not only decreases the amount of Ras in the membrane but also generates a cytosolic pool of Ras. In tumor cells having activated Ras, the cytosolic pool acts as another antagonist of membrane-bound Ras function. In normal cells having normal Ras, the cytosolic pool of Ras does not act as an antagonist. In the absence of complete inhibition of farnesylation, other farnesylated proteins are able to continue with their functions.

Farnesyl-protein transferase activity may be reduced or completely inhibited by adjusting the compound dose. Reduction of farnesyl-protein transferase enzyme activity by adjusting the compound dose would be useful for avoiding possible undesirable side effects resulting from interference with other metabolic processes which utilize the enzyme.

These compounds and their analogs are inhibitors of farnesyl-protein transferase. Farnesyl-protein transferase utilizes farnesyl pyrophosphate to covalently modify the Cys thiol group of the Ras CAAX box with a farnesyl group. Inhibiting HMG-CoA reductase blocks Ras membrane localization in vivo and inhibits Ras function. Inhibition of farnesyl-protein transferase is more specific and is attended by fewer side effects than is the case for a general inhibitor of isoprene biosynthesis.

Previously, it has been demonstrated that tetrapeptides containing cysteine as an amino terminal residue with the CAAX sequence inhibit Ras farnesylation (Schaber et al., ibid; Reiss et. al., ibid; Reiss et al., PNAS, 88: 732-736 (1991)). Such inhibitors may inhibit while serving as alternate substrates for the Ras farnesyltransferase enzyme, or may be purely competitive inhibitors (U.S. Pat. No. 5,141,851, University of Texas).

The compounds of the present invention are peptide analogs containing two reduced peptide bonds and of the general structure C--[ψCH₂ NH]Xaa¹ --[ψCH₂ NR] Xaa² --Xaa³ where C is Cysteine and Xaa¹⁻³ is any amino acid and the nitrogen between Xaa¹ and Xaa² is alkylated. The compounds of this invention are stable inhibitors of Ras farnesyl-transferase. The presence of the reduced amide linkages confers metabolic stability to these inhibitors such that they are capable of inhibiting ras farnesylation in vivo. Reduction of the first and second peptide bonds may also lead to an unexpected enhancement of intrinsic enzyme-inhibitory activity. Alkylation of the reactive nitrogen between Xaa¹ and Xaa² confers chemical stability to these analogs, thus enhancing their activity in vivo (cell culture). Of particular utility is the observation that the lactone or ester forms of these inhibitors are prodrugs that efficiently deliver the active hydroxy acids or acids, respectively, to the intracellular compartment that is the site of Ras farnesylation.

It is, therefore, an object of this invention to develop tetrapeptide-based compounds with two reduced amide linkages, wherein the nitrogen between Xaa¹ and Xaa² is alkylated, and which will inhibit farnesyl-protein transferase and the farnesylation of the oncogene protein Ras. It is a further object of this invention to develop chemotherapeutic compositions containing the compounds of this invention, and methods for producing the compounds of this invention.

SUMMARY OF THE INVENTION

The present invention includes tetrapeptide analogs which possess two reduced amide linkages and which inhibit farnesyl-protein transferase and the farnesylation of the oncogene protein Ras, chemotherapeutic compositions containing the compounds of this invention, and methods for producing the compounds of this invention.

The compounds of this invention are illustrated by the formulae: ##STR1##

DETAILED DESCRIPTION OF THE INVENTION

The compounds of this invention are useful in the inhibition of farnesyl-protein transferase and the farnesylation of the oncogene protein Ras. In s first embodiment of this invention the inhibitors of farnesyl-protein transferase are illustrated by the formula I: ##STR2## wherein: R¹ is hydrogen, an alkyl group, an aralkyl group, an acyl group, an aracyl group, an aroyl group, an alkylsulfonyl group, aralkylsulfonyl group or arylsulfonyl group, wherein alkyl and acyl groups comprise straight chain or branched chain hydrocarbons of 1 to 6 carbon atoms;

R², R³ and R⁴ are the side chains of naturally occurring amino acids, including their oxidized forms which may be methionine sulfoxide or methionine sulfone, or in the alternative may be substituted or unsubstituted aliphatic, aromatic or heteroaromatic groups, such as allyl, cyclohexyl, phenyl, pyridyl, imidazolyl or saturated chains of 2 to 8 carbon atoms which may be branched or unbranched, wherein the aliphatic substituents may be substituted with an aromatic or heteroaromatic ring;

R⁵ is an alkyl group, wherein the alkyl group comprises straight chain or branched chain hydrocarbons of 1 to 6 carbon atoms, which may be substituted with an aromatic or heteroaromatic group;

and the pharmaceutically acceptable salts thereof.

In a second embodiment of this invention the prodrugs of compounds of formula I are illustrated by the formula II: ##STR3## wherein: R¹ is hydrogen, an alkyl group, an aralky group, an acyl group, an aracyl group, an aroyl group, an alkylsulfonyl group, aralkylsulfonyl group or arylsulfonyl group, wherein alkyl and acyl groups comprise straight chain or branched chain hydrocarbons of 1 to 6 carbon atoms;

R², R³ and R⁴ are the side chains of naturally occurring amino acids, including their oxidized forms which may be methionine sulfoxide or methionine sulfone, or in the alternative may be substituted or unsubstituted aliphatic, aromatic or heteroaromatic groups, such as allyl, cyclohexyl, phenyl, pyridyl, imidazolyl or saturated chains of 2 to 8 carbon atoms which may be branched or unbranched, wherein the aliphatic substituents may be substituted with an aromatic or heteroaromatic ring;

R⁵ is an alkyl group, wherein the alkyl group comprises straight chain or branched chain hydrocarbons of 1 to 6 carbon atoms, which may be substituted with an aromatic or heteroaromatic group;

R⁶ is a substituted or unsubstituted aliphatic, aromatic or heteroaromatic group such as saturated chains of 1 to 8 carbon atoms, which may be branched or unbranched, wherein the aliphatic substituent may be substituted with an aromatic or heteroaromatic ring;

and the pharmaceutically acceptable salts and disulfides thereof.

In a third embodiment of this invention, the inhibitors of farnesyl-protein transferase are illustrated by the formula III: ##STR4## wherein: R¹ is hydrogen, an alkyl group, an aralkyl group, an acyl group, an aracyl group, an aroyl group, an alkylsulfonyl group, aralkylsulfonyl group or arylsulfonyl group, wherein alkyl and acyl groups comprise straight chain or branched chain hydrocarbons of 1 to 6 carbon atoms;

R² and R³ are the side chains of naturally occurring amino acids, including their oxidized forms which may be methionine sulfoxide or methionine sulfone, or in the alternative may be substituted or unsubstituted aliphatic, aromatic or heteroaromatic groups, such as allyl, cyclohexyl, phenyl, pyridyl, imidazolyl or saturated chains of 2 to 8 carbon atoms which may be branched or unbranched, wherein the aliphatic substituents may be substituted with an aromatic or heteroaromatic ring;

R⁵ is an alkyl group, wherein the alkyl group comprises straight chain or branched chain hydrocarbons of 1 to 6 carbon atoms, which may be substituted with an aromatic or heteroaromatic group;

n is 0, 1 or 2;

and the pharmaceutically acceptable salts thereof.

In a fourth embodiment of this invention the prodrugs of compounds of formula III are illustrated by the formula IV: ##STR5## wherein: R¹ is hydrogen, an alkyl group, an aralkyl group, an acyl group, aracyl group, an aroyl group, an alkylsulfonyl group, aralkylsulfonyl group or arylsulfonyl group, wherein alkyl and acyl groups comprise straight chain or branched chain hydrocarbons of 1 to 6 carbon atoms;

R² and R³ are the side chains of naturally occurring amino acids, including their oxidized forms which may be methionine sulfoxide or methionine sulfone, or in the alternative may be substituted or unsubstituted aliphatic, aromatic or heteroaromatic groups, such as allyl, cyclohexyl, phenyl, pyridyl, imidazolyl or saturated chains of 2 to 8 carbon atoms which may be branched or unbranched, wherein the aliphatic substituents may be substituted with an aromatic or heteroaromatic ring;

R⁵ is an alkyl group, wherein the alkyl group comprises straight chain or branched chain hydrocarbons of 1 to 6 carbon atoms, which may be substituted with an aromatic or heteroaromatic group;

and the pharmaceutically acceptable salts and disulfides thereof.

The preferred compounds of this invention are as follows:

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-homoserine,

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-homoserine lactone,

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-phenylalanyl-homoserine,

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-phenylalanyl-homoserine lactone,

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3-methylbutyl]-N-methyl-phenylalanyl-homoserine,

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3-methylbutyl]-N-methyl-phenylalanyl-homoserine lactone,

3(S)-{N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucylamino}-3-methyltetrahydropyran-2-one,

2(S)-{N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucylamino}-2-methyl-5-hydroxypentanoic acid,

2(S)-{N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucylamino}-5-methyl-5-hydroxyhexanoic acid,

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-norvalyl-homoserine,

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-norvalyl-homoserine lactone,

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-methionine,

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-methionine methyl ester,

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-phenylalanyl-methionine,

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-phenylalanyl-methionine methyl ester,

3(S)-{N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucylamino}-6,6-dimethyltetrahydropyran-2-one,

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-norvalyl-methionine,

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-norvalyl-methionine methyl ester,

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-D-norvalyl-homoserine, or

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-D-norvalyl-homoserine lactone,

and the pharmaceutically acceptable salts thereof.

The most preferred compounds of this invention include the following inhibitor and corresponding ester/lactone prodrug pairs:

N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-homoserine ##STR6## N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-homoserine lactone ##STR7## N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-methionine ##STR8## N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methyl pentyl]-N-methyl-isoleucyl-methionine methyl ester ##STR9## and the pharmaceutically acceptable salts thereof.

In the present invention, the amino acids which are disclosed are identified both by conventional 3 letter and single letter abbreviations as indicated below:

    ______________________________________                                         Alanine           Ala    A                                                     Arginine          Arg    R                                                     Asparagine        Asn    N                                                     Aspartic acid     Asp    D                                                     Asparagine or     Asx    B                                                     Aspartic acid                                                                  Cysteine          Cys    C                                                     Glutamine         Gln    Q                                                     Glutamic acid     Glu    E                                                     Glutamine or      Glx    Z                                                     Glutamic acid                                                                  Glycine           Gly    G                                                     Histidine         His    H                                                     Isoleucine        Ile    I                                                     Leucine           Leu    L                                                     Lysine            Lys    K                                                     Methionine        Met    M                                                     Phenylalanine     Phe    F                                                     Proline           Pro    P                                                     Serine            Ser    S                                                     Threonine         Thr    T                                                     Tryptphan         Trp    W                                                     Tyrosine          Tyr    Y                                                     Valine            Val    V                                                     ______________________________________                                    

The pharmaceutically acceptable salts of the compounds of this invention include the conventional non-toxic salts of the compounds of this invention as formed, e.g., from non-toxic inorganic or organic acids. For example, such conventional non-toxic salts include those derived from inorganic acids such as hydrochloric, hydrobromic, sulfuric, sulfamic, phosphoric, nitric and the like: and the salts prepared from organic acids such as acetic, propionic, succinic, glycolic, stearic, lactic, malic, tartaric, citric, ascorbic, pamoic, maleic, hydroxymaleic, phenylacetic, glutamic, benzoic, salicylic, sulfanilic, 2-acetoxy-benzoic, fumaric, toluenesulfonic, methanesulfonic, ethane disulfonic, oxalic, isethionic, trifluoroacetic and the like.

The pharmaceutically acceptable salts of the compounds of this invention can be synthesized from the compounds of this invention which contain a basic moiety by conventional chemical methods. Generally, the salts are prepared by reacting the free base with stoichiometric amounts or with an excess of the desired salt-forming inorganic or organic acid in a suitable solvent or various combinations of solvents.

The compounds of the invention can be synthesized from their constituent amino acids by conventional peptide synthesis techniques, and the additional methods described below. Standard methods of peptide synthesis are disclosed, for example, in the following works: Schroeder et al., "The Peptides", Vol. I, Academic Press 1965, or Bodanszky et al., "Peptide Synthesis", Interscience Publishers, 1966, or McOmie (ed.) "Protective Groups in Organic Chemistry", Plenum Press, 1973, or Barany et al., "The Peptides: Analysis, Synthesis, Biology" 2, Chapter 1, Academic Press, 1980, or Stewart et al., "Solid Phase Peptide Synthesis", Second Edition, Pierce Chemical Company, 1984. The teachings of these works are hereby incorporated by reference.

Compounds of this invention are prepared by employing reactions A through C as shown in the Reaction Scheme, in addition to other standard manipulations such as ester hydrolysis, cleavage of protecting groups, etc., as may be known in the literature or exemplified in the experimental procedures. The key bond-forming reactions are:

Reaction A: Amide bond formation and protecting group cleavage using standard solution or solid phase methodologies.

Reaction B: Preparation of a reduced peptide subunit by reductive alkylation of an amine by an aldehyde using sodium cyanoborohydride or other reducing agents.

Reaction C; Alkylation of a reduced peptide subunit with an alkyl or aralkyl halide or, alternatively, reductive alkylation of a reduced peptide subunit with an aldehyde using sodium cyanoborohydride or other reducing agents.

These reactions may be employed in a linear sequence to provide the compounds of the invention or they may be used to synthesize fragments which are subsequently joined by the alkylation reactions described in the Reaction Scheme.

REACTION SCHEME A Reaction A Coupling of residues to form an amide bond ##STR10## Reaction B Preparation of reduced peptide subunits by reductive alkylation ##STR11## REACTION SCHEME C Reaction C Alkylation/reductive alkylation of reduced peptide subunits ##STR12## where R^(A) and R^(B) are R², R³ or R⁴ as previously defined; X is a leaving group, e.g., Br⁻, I⁻ or MsO⁻ ; and R⁷ is defined such that R⁵ is generated by the reductive alkylation process.

The compounds of this invention inhibit farnesyl-protein transferase and the farnesylation of the oncogene protein Ras. These compounds are useful as pharmaceutical agents for mammals, especially for humans. These compounds may be administered to patients for use in the treatment of cancer. Examples of the type of cancer which may be treated with the compounds of this invention include, but are not limited to, colorectal carcinoma, exocrine pancreatic carcinoma, and myeloid leukemias.

The compounds of this invention may be administered to mammals, preferably humans, either alone or, preferably, in combination with pharmaceutically acceptable carriers or diluents, optionally with known adjuvants, such as alum, in a pharmaceutical composition, according to standard pharmaceutical practice. The compounds can be administered orally or parenterally, including the intravenous, intramuscular, intraperitoneal, subcutaneous, rectal and topical routes of administration.

For oral use of a chemotherapeutic compound according to this invention, the selected compound may be administered, for example, in the form of tablets or capsules, or as an aqueous solution or suspension. In the case of tablets for oral use, carriers which are commonly used include lactose and corn starch, and lubricating agents, such as magnesium stearate, are commonly added. For oral administration in capsule form, useful diluents include lactose and dried corn starch. When aqueous suspensions are required for oral use, the active ingredient is combined with emulsifying and suspending agents. If desired, certain sweetening and/or flavoring agents may be added. For intramuscular, intraperitoneal, subcutaneous and intravenous use, sterile solutions of the active ingredient are usually prepared, and the pH of the solutions should be suitably adjusted and buffered. For intravenous use, the total concentration of solutes should be controlled in order to render the preparation isotonic.

The present invention also encompasses a pharmaceutical composition useful in the treatment of cancer, comprising the administration of a therapeutically effective amount of the compounds of this invention, with or without pharmaceutically acceptable carriers or diluents. Suitable compositions of this invention include aqueous solutions comprising compounds of this invention and pharmacalogically acceptable carriers, e.g., saline, at a pH level, e.g., 7.4. The solutions may be introduced into a patient's intramuscular blood-stream by local bolus injection.

When a compound according to this invention is administered into a human subject, the daily dosage will normally be determined by the prescribing physician with the dosage generally varying according to the age, weight, and response of the individual patient, as well as the severity of the patient's symptoms.

In one exemplary application, a suitable amount of compound is administered to a mammal undergoing treatment for cancer. Administration occurs in an amount between about 0.1 mg/kg of body weight to about 20 mg/kg of body weight per day, preferably of between 0.5 mg/kg of body weight to about 10 mg/kg of body weight per day.

EXAMPLES

Examples provided are intended to assist in a further understanding of the invention. Particular materials employed, species and conditions are intended to be further illustrative of the invention and not limitative of the reasonable scope thereof.

EXAMPLE 1 Preparation of N-[2(S)-(2(R)-Amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-homoserine lactone and N-[2(S)-(2(R)-Amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-homoserine

Step A: N-(t-butoxycarbonyl)-isoleucine aldehyde

This compound was synthesized by applying the procedure of Goel, Krolls, Stier, and Kesten [Organic Syntheses, 67, 69 (1989)] to N-(t-butoxycarbonyl)-isoleucine. The compound was obtained as a colorless oil, which was used without purification.

Step B: N-[(2S)-(t-Butoxycarbonylamino)-3(S)-methylpentyl]-isoleucine benzyl ester

N-(t-Butoxycarbonyl)-isoleucine aldehyde (8.0 g, 0.037 mol) and isoleucine benzyl ester p-toluenesulfonate salt (19.0 g, 0.048 mol) were dissolved in MeOH (50 mL) at ambient temperature under nitrogen and treated with 3A molecular sieves (15 g) and sodium triacetoxyborohydride (20.4 g, 0.096 mol) with stirring. After 2 h the mixture was filtered, concentrated, and the residue was partitioned between EtOAc (100 mL) and satd aq NaHCO₃ soln (100 mL). The basic layer was washed with EtOAc (2×50 mL), the organics combined, washed with brine, and dried (Na₂ SO₄). Filtration and concentration to dryness gave 6.4 g (41%) of the title compound as a white solid after chromatography (SiO₂, hexane: EtOAc, 9:1). ¹ NMR (CD₃ OD) δ 7.30-7.45 (m, 5H), 5.18 (ABq, 2H), 3.40-3.45 (m, 1H), 3.12 (d, 1H, J=6 Hz), 2.70 (dd, 1H, J=4, 12 Hz), 2.37 (dd, 1H, J=4, 12 Hz), 2.63-2.76 (m, 1 H), 1.45-1.61 (m, 2H), 1.46 (s, 9H), 1.05-1.26 (m, 2H), 0.82-0.95 (m, 12H).

Step C: N-[(2S)-(t-Butoxycarbonylamino)-3(S)-methylpentyl]-N-methyl-isoleucine benzyl ester

N-[(2S)-(t-Butoxycarbonylamino)-3(S)-methylpentyl]-isoleucine benzyl ester (0.8 g, 1.9 mmol) was dissolved in acetone (3 mL), treated with K₂ CO₃ (0.52 g, 3.8 mmol) and iodomethane (1.2 mL, 19 mmol) and stirred for 18 h at ambient temperature. The reaction mixture was treated with 5% aq NH₄ OH soln (10 mL), stirred for 0.5 h, concentrated, and partitioned between EtOAc (20 mL) and H₂ O (20 mL). The aq layer was washed with EtOAc (2×20 mL), organics combined, washed sequentially with H₂ O, 10% citric acid, brine, and dried (Na₂ SO₄). Filtration and concentration to dryness gave 0.814 g (98%) of the title compound as a yellow oil. ¹ H NMR (CDCL₃) δ 7.32-7.41 (m, 5H), 5.11-5.24 (m, 2H), 3.58-3.72 (m, 1H), 2.8-3.0 (m, 1H), 2.20-2.65 (m, 5H), 1.88-2.0 (m, 1H), 1.68-1.80 (m, 1H), 1.56-1.67 (m, 1H), 1.45 (s, 9H), 1.29-1.42 (m, 2H), 1.12-1.28 (m, 1H), 0.98-1.09 (m, 1H), 0.80-0.95 (m, 12H).

Step D: N-[(2S)-(t-Butoxycarbonylamino)-3(S)-methylpenyl]-N-methyl-isoleucine

N-[(2S)-(t-Butoxycarbonylamino)-3(S)-methylpentyl]-N-methyl-isoleucine benzyl ester (0.814 g, 1.87 mmol) was dissolved in methanol (25 mL)-EtOAc (25 mL), treated with 10% palladium on carbon (0.1 g) and hydrogenated under a balloon of hydrogen for 4 h. Filtration and concentration to dryness gave 0.614 g (95%) of the title compound as a white solid. ¹ H NMR (CDCl₃) δ 5.1-5.2 (m, 1H), 3.7-3.8 (m, 1H), 3.27-3.35 (m, 1H), 2.8-2.92 (m, 2H), 2.55 (s, 3H), 1.80-1.93 (m, 1H), 1.55-1.8 (m, 2H), 1.48 (s, 9H), 1.23-1.42 (m, 1H), 1.05-1.2 (m, 1H), 0.82-1.03 (m, 12H).

Step E: N-[2(S)-(t-butoxycarbonylamino-3(S)-methylpentyl]-N-methyl-isoleucyl-homoserine lactone

N-[(2S)-(t-Butoxycarbonylamino)-3(S)-methylpentyl]-N-methyl-isoleucine (1.05 g, 3.05 mmol) was dissolved in DMF (10 mL) with stirring at ambient temperature and treated with EDC (0.64 g, 3.35 mmol), HOBT (0.45 g, 3.35 mmol), and homoserine lactone hydrochloride. The pH was adjusted to 6 with Et₃ N (0.40 mL, 2.9 mmol) and stirring was continued for 18 h. The reaction mixture was concentrated, then partitioned between EtOAc (50 mL)-H₂ O (50 mL). The aq layer was washed with EtOAc (3×20 mL), the organics combined, washed with aq satd NaHCO₃ soln, brine, and dried (Na₂ SO₄). Filtration and concentration gave 0.78 g (60%) of the title compound after chromatography (SiO₂, hexane: EtOAc, 3:1 to 2:1 to EtOAc). ¹ H NMR (CD₃ OD) δ 4.59 (t, 1H, J=10 Hz), 4.47 (td, 1H, J=2, 10 Hz), 4.28-4.39 (m, 2H), 3.56-3.64 (m, 1H), 2.74 (d, 1H, J=10 Hz), 2.5-2.7 (m, 2H), 2.3-2.42 (m, 2H), 2.29 (s, 3H), 1.75-1.92 (m, 2H), 1.4-1.6 (m, 2H), 1.46 (s, 9H), 1.07-1.20 (m, 2H), 0.88-0.95 (m, 12H).

Step F: N-[2(S)-amino-3(S)-methylpentyl]-N-methylisoleucyl-homoserine lactone

HCl gas was bubbled into a solution of N-[2(S)-(t-butoxycarbonylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-homoserine lactone (0.21 g, 0.5 mmol) in EtOAc (50 mL) with stirring at -20° C. over 0.5 h. The soln was purged with argon for 0.5 h, then concentrated to give 0.21 g (100%) of the title compound as a white solid. ¹ H NMR (CD₃ OD) δ 4.46-5.05 (m, 2H), 4.28-4.38 (m, 1H), 3.54-3.70 (m, 2H), 3.2-3.4 (m, 2H), 2.75-2.97 (m, 3H), 2.45-2.59 (m, 2H), 2.1-2.2 (m, 1H), 1.72-1.92 (m, 2H), 1.50-11.63 (m, 1H), 1.18-1.4 (m, 2H), 0.98-1.12 (m, 12H).

Step G: Preparation of N-(t-butoxycarbonyl)-S-triphenylmethyl cysteine aldehyde

This compound was synthesized by applying the procedure of Goel, Krolls, Stier, and Kesten [Organic Syntheses, 67, 69(1988)] to N-(t-butoxycarbonyl)-S-trityl cysteine. The compound was obtained as a white solid, which was used without purification. ¹ H NMR (CDCl₃) d 9.2 (1H, s), 7.5-7.1 (18H, m), 5.1 (1H, br d), 3.92 (1H, m), 2.85-2.5 (2H, m), 1.4 (9H, s).

Step H: N-[2(S)-(2(R)-(t-butoxycarbonylamino)-3-triphenylmethyl mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-homoserine lactone

N-[2(S)-amino-3(S)-methylpentyl]-N-methylisoleucyl-homoserine lactone (0.21 g, 0.6 mmol) was dissolved in methanol (3 mL), treated with KOAc (0.1 g, 1.0 mmol), 3A molecular sieves (0.5 g), and N-(t-butoxycarbonylamino)-S-triphenylmethylcysteine aldehyde (0.25 g, 0.6 mmol) followed by sodium cyanoborohydride (1M in THF) (1 mL) and stirred at ambient temperature for 18 h. The reaction mixture was filtered and partitioned between EtOAc (20 mL) and aq satd NaHCO₃ soln. The organic layer was washed with brine and dried (Na₂ SO₄). Filtration and concentration to dryness gave a solid product which was chromatographed (SiO₂, CH₂ Cl₂ : MeOH, 99:1 to 97:3) to give 0.12 g (33%) of the title compound. ¹ H NMR (CD₃ OD) δ 7.21-7.42 (m, 15H), 4.42-4.56 (m, 2H), 4.25-4.34 (m, 1H), 3.62-3.72 (m, 1H), 2.63-2.80 (m, 3H), 2.30-2.60 (m, 6H), 2.18-2.28 (m, 4H), 1.81-1.93 (m, 1H), 1.54-1.78 (m, 2H), 1.45 (s, 9h), 1.06-1.37 (m, 3H), 0.80-0.98 (m, 12H).

Step I: N-[2(S)-(2(R)-Amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucylhomoserine lactone

N-[2(S)-(2(R)-(t-butoxycarbonylamino)-3-triphenylmethyl mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-homoserine lactone (0.12 g, 0.16 mmol) was dissolved in CH₂ Cl₂ (5 mL), treated with CF₃ CO₂ H (TFA) (2.5 mL) and triethylsilane (0.10 mL, 0.64 mmol), and stirred at ambient temperature for 0.5 h. The soln was concentrated to dryness and triturated with 0.1% TFA in H₂ O. The solid triphenylmethane was removed by filtration and the filtrate was lyophilized to give 0.07 g (59%) of the title compound. ¹ H NMR (CD₃ OD) δ 4.45-4.55 (m, 2H), 4.28-4.35 (m, 1H), 3.52-3.61 (m, 1H), 3.49 (d, 1H, J=6 Hz), 3.18-3.25 (m, 1H), 3.02-3.16 (m, 4H), 2.92 (t, 1H, J=6 Hz), 2.85 (t, 1H, J=6 Hz), 2.78 (s, 3H), 2.42-2.56 (m, 2H), 2.05-2.15 (m, 1H), 1.83-1.94 (m, 1H), 1.58-1.61 (m, 1H), 1.40-1.52 (m, 1H), 1.22-1.4 (m, 2H), 0.93-1.06 (m, 12H).

Anal. Calcd for C₂₀ H₄₀ N₄ O₃ S.3CF₃ CO₂ H.0.6 H₂ O: C, 40.72; H, 5.77; N, 7.31. Found: C, 40.72; H, 5.99; N, 7.69.

Step J: N-[2(S)-(2(R)-Amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucylhomoserine

N-[2(S)-(2(R)-Amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-homoserine lactone (0.0025 g, 0.00326 mmol) was dissolved in MeOH (0.0506 mL) and 1N NaOH (0.0134 mL) was added followed by MeOH (0.262 mL). Conversion of the lactone to the hydroxy-acid was confirmed by HPLC analysis and/or ¹ H NMR spectroscopy.

EXAMPLE 2 Preparation of N-[2(S)-(2(R)-Amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-phenylalanylhomoserine lactone and N-[2(S)-(2(R)-Amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-phenylalanylhomoserine

The title compounds were prepared according to the methods of Example 1, substituting phenylalanine methyl ester for the isoleucine benzyl ester used in Step B. Step D was replaced by a hydrolysis of the methyl ester as outlined below.

Step D: N-[(2S)-(t-Butoxycarbonylamino)-3(S)-methylpentyl]-N-methyl-phenylalanine

N-[(2S)-(t-Butoxycarbonylamino)-3(S)-methylpentyl]-N-methyl-phenylalanine methyl ester (1.92 g, 0.0049 mol) was dissolved in MeOH (20 mL), treated with 4 equivalents of 1N NaOH (19.56 mL, 0.0196 mol), and stirred at ambient temperature for 18 h. The reaction mixture was concentrated to remove the methanol, then neutralized with 1N HCl (19.56 mL, 0.0196 mol), and extracted with EtOAc (3×30 mL). The organics were combined, washed with brine and dried (Na₂ SO₄). Filtration and concentration to dryness gave 1.6 g (86%) of the title compound which was used without further purification. Using Steps E-I of Example 1, the title compound was obtained as its trifluoroacetate salt, mp 74°-80° C. ¹ H NMR (CD₃ OD) d 7.2-7.4 (m, 5H), 4.41-4.48 (m, 1H), 4.24 (q, 1H, J=9 Hz), 4.15 (t, 1H, 11 Hz), 3.97 (dd, 1H, J=6, 11 Hz), 3.53 (t, 1H, J=6 Hz), 2.95-3.4 (m, 8H), 2.82-2.92 (m, 1H), 2.81 (s, 3H), 2.12-2.3 (m, 2H), 1.82-1.95 (m, 1H), 1.35-1.52 (m, 1H), 1.15-1.23 (m, 1H), 0.85-1.03 (m, 6H). Anal. Calculated for C₂₃ H₃₈ N₄ O₃ S . 2.85 CF₃ CO₂ H: C, 44.44; H, 5.31; N, 7.22; Found: C, 44.36; H, 5.46; N, 7.50.

The lactone was converted to the hydroxy acid by the method of Example 1, Step J.

EXAMPLE 3 Preparation of N-[2(S)-(2(R)-Amino-3-mercaptopropylamino)-3-methylbutyl]-N-methyl-phenylalanyl-homoserine lactone and N-[2(S)-(2(R)-Amino-3-mercaptopropylamino)-3-methylbutyl]-N-methyl-phenylalanyl-homoserine

The title compounds were prepared according to the methods of Example 1 and 2, substituting N-t-butoxycarbonylvaline for the isoleucine derivative used in Step A. The homoserine lactone was obtained as its trifluoroacetate salt, mp 55°-60° C. ¹ H NMR (CD₃ OD) δ 7.21-7.39 (m, 5H), 4.43 (td, 1H, J=4, 10 Hz), 4.22 (q, 1H, J=9 Hz), 4.12 (t, 1H, J=10 Hz), 3.50-3.58 (m, 1H), 3.02-3.35 (m, 8H), 2.82-2.90 (m, 2H), 2.82 (s, 3H), 2.04-2.28 (m, 3H), 1.05 (d, 3H, J=6 Hz), 0.98 (d, 3H, J=6 Hz). Anal. calculated for C₂₂ H₃₆ N₄ O₃ S.3 CF₃ CO₂ H.H₂ O: C, 42.21; H, 5.19; N, 7.03; Found: C, 42.17 ; H, 5.03; N, 7.26.

The hydroxy acid was generated in situ according to Example 1, Step J.

EXAMPLE 4 N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-norvalyl-homoserine lactone and N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-norvalyl-homoserine

The title compounds were prepared according to the methods of Examples 1 and 2, substituting norvaline methyl ester for the isoleucine benzyl ester used in Step B. The homoserine lactone was obtained as its trifluoroacetate salt, mp 50°-55° C. ¹ H NMR (CD₃ OD) δ 4.45-4.51 (m, 2H), 4.25-4.38 (m, 1H), 3.75-3.82 (m, 1H), 3.43 (t, 1H, J=6 Hz), 2.82-3.15 (m, 7H), 2.88 (s, 3H), 2.4-2.55 (m, 2H), 1.78-1.97 (m, 3H), 1.32-1.48 (m, 3H), 1.15-1.32 (m, 1H), 1.01 (q, 6H, J=9 Hz), 1.90 (d, 3H, J=7 Hz).

Anal. calculated for C₁₉ H₃₈ N₄ O₃ S. 3CF₃ CO₂ H .0.75 H₂ O: C, 39.60; H, 5.65; N, 7.39; Found: C, 49.58; H, 5.65; N, 7.48.

The hydroxy acid was generated in situ according to Example 1, Step J.

EXAMPLE 5 N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-methionine methyl ester

The title compound was prepared according to the methods of Example 1, Steps A-I, substituting methionine methyl ester for homoserine lactone in Step E. The trifluoroacetate salt was obtained after lyophilization. ¹ H NMR (CD₃ OD) δ 4.65-4.73 (m, 1H), 3.75 (s, 3H), 3.42-3.54 (m, 2H), 2.87-3.22 (m, 7H), 2.73 (s, 3H), 2.49-2.58 (m, 2H), 2.12-2.25 (m, 1H), 2.10 (s, 3H), 1.98-2.1 (m, 2H), 1.8-1.92 (m, 1H), 1.62-1.77 (m, 1H), 1.21-1.48 (m, 3H), 0.9-1.05 (m, 12H).

Anal. calculated for C₂₂ H₄₆ N₄ O₃ S₂.2.25 CF₃ CO₂ H: C, 43.28; H, 6.61; N, 7.62; Found: C, 43.23; H, 6.54; N, 7.81.

EXAMPLE 6 N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-methionine

Step A: N-[2(S)-(2(R)-(t-butoxycarbonylamino-3-triphenylmethylmercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-methionine

N-[2(S)-(2(R)-(t-butoxycarbonylamino-3-triphenylmethyl mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-methionine methyl ester (0.19 g, 0.232 mmol, prepared as an intermediate in Example 5) was dissolved in MeOH (4 mL), treated with 1N NaOH soln (0.927 mL, 0.927 mmol), and stirred for 3.5 h at ambient temperature. The reaction mixture was concentrated, the residue dissolved in H₂ O (20 mL), neutralized with 1N HCl (0.927 mL, 0.927 mmol), and extracted with EtOAc (3×20 mL). The organic layers were combined, washed with brine, and dried (Na₂ SO₄). Filtration and concentration to dryness gave 0.18 g (96%) of the title compound which was used without further purification.

Step B: N-[2(S)-(2(R)-amino-3-mercaptopropylamino)3(S)-methylpentyl]-N-methyl-isoleucylmethionine

N-[2(S)-(2(R)-(t-butoxycarbonylamino-3-triphenylmethylmercaptopropylamino)-3(S)-methylpentyl]N-methyl-isoleucyl-methionine (0.18 g, 0.223 mmol) was dissolved in CH₂ Cl₂ (4 mL), treated with CF₃ CO₂ H (2 mL) and triethylsilane (0.143 mL, 0.893 mmol) and stirred at ambient temperature for 1.5 h. The reaction mixture was concentrated, partitioned between hexane (20 mL) and 0.1% TFA in H₂ O (20 mL), the aqueous layer lyophilized to give crude product which was purified by preparative HPLC and re-lyophilized to give 0.075 g (43%) of the title compound as the trifluoroacetate salt. ¹ H NMR (CD₃ OD) δ 4.59-4.68 (m, 1H), 3.47-3.6 (m, 2H), 3.16 (d, 1H, J=6 Hz), 3.06 (s, 3H), 2.85-3.03 (m, 3H), 2.77 (s, 3H), 2.5-2.7 (m, 2H), 2.17-2.29(m, 1H), 2.11 (s, 3H), 1.98-2.1 (m, 2H), 1.8-1.93 (m, 1H), 1.58-1.75 (m, 1H), 1.2-1.5 (m, 3H), 0.85-1.05 (m, 12H).

Anal. calculated for C₂₁ H₄₄ N₄ O₃ S₂.2.75 CF₃ CO₂ H C, 40.89; H, 6.05; N, 7.20; Found: C, 41.18; H, 6.21; N, 7.25.

EXAMPLE 7 N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-phenylalanyl-methionine methyl ester

The title compound was prepared according to the methods of Example 5, substituting phenylalanine methyl ester for isoleucine benzyl ester is Step B, and isolated as its trifluoroacetate salt. ¹ H NMR (CD₃ OD) δ 7.26-7.37 (m, 5H), 4.49-4.55 (m, 1H), 4.16 (t, 1H, J=8 Hz), 3.70 (s, 3H), 3.53 (t, 1H, J=6 Hz), 2.9-3.3 (m, 7H), 2.89 (d, 2H, J=6 Hz), 2.70 (s, 3H), 2.24-2.6 (m, 2H), 2.05 (s, 3H), 1.8-2.17 (m, 3H), 1.33-1.48 (m, 1H), 1.18-1.3 (m, 1H), 0.9-1.0 (m, 6H). MS (M+1) 513.

EXAMPLE 8 N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-phenylalanyl-methionine

The title compound was prepared via an intermediate obtained in Example 7, according to the methods of Example 6 and isolated as its trifluoroacetate salt.

¹ H NMR (CD₃ OD) δ 7.24-7.4 (m, 5H), 4.4-4.5 (m, 1H), 4.12 (t, 1H, J=8 Hz), 3.45-3.52 (m, 1H) 2.8-3.25 (m, 7H), 2.66 (s, 3H), 2.6-2.7 (m, 1H), 2.23-2.5 (m, 2H), 2.05-2.2 (m, 1H), 2.04 (s, 3H), 1.9-2.04 (m, 2H), 1.76-1.9 (m, 1H), 1.12-1.46 (m, 2H), 0.85-1.0 (m, 6H).

Anal. calculated for C₂₄ H₄₂ N₄ O₃ S₂.3CF₃ CO₂ H.0.5 CH₃ CN: C, 43.22; H, 5.44; N, 7.32; Found: C, 43.22; H, 5.67; N, 7.68.

EXAMPLE 9 N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-norvalyl-methionine methyl ester

The title compound was prepared according to the methods of Examples 1 and 2, substituting norvaline methyl ester for isoleucine benzyl ester in Step B, methionine methyl ester for homoserine lactone in Step E and substituting the following alternative procedure for Step C.

Step C: N-[(2S)-(t-Butoxycarbonylamino)-3(S)-methylpentyl]-N-methyl-norvaline methyl ester

N-[(2S)-(t-Butoxycarbonylamino)-3(S)-methylpentyl]-norvaline methyl ester (1.15 g, 3.6 mmol) was dissolved in MeOH (15 mL), treated with acetic acid (0.21 mL, 3.6 mmol), formaldehyde (37% in H₂ O) (0.61 mL, 7.2 mmol) and sodium cyanoborohydride (0.34 g, 5.4 mmol) with stirring under argon at ambient temperature. After 4 h the reaction mixture was concentrated, partitioned between EtOAc (20 mL)- aq satd NH₄ OH soln (20 mL), and the organic layer dried (Na₂ SO₄) and concentrated to give 1.03 g (83%) of the title compound as a colorless oil. ¹ H NMR (CD₃ OD) δ 3.68 (s, 3H), 3.52-3.6 (m, 1H), 3.27 (t, 1H, J=8 Hz), 2.66 (dd, 1H, J=5, 12 Hz), 2.42 (dd, 1H, J=5, 12 Hz), 2.28 (s, 3H), 1.57-1.69 (m, 3H), 1.44 (s, 9H), 1.2-1.5 (m, 3H), 1.0-1.2 (m, 1H), 0.86-1.0 (m 9H).

Following Example 1, Steps D through I, the title compound was isolated as its hydrochloride salt. ¹ H NMR (CD₃ OD) δ 4.66-4.72 (m, 1H), 3.89-3.95 (m, 1H), 3.74 (s, 3H), 3.45-3.6 (m, 1H), 3.1-3.4 (m, 4H), 2.94 (s, 3H), 2.89-3.2 (m, 3H), 2.58-2.73 (m, 2H), 2.12 (s, 3H), 1.88-2.25 (m, 4H), 1.2-1.65 (m, 5H), 0.91-1.1 (m, 9H).

Anal. caculated for C₂₁ H₄₄ N₄ O₃ S₂.4.5 HCl: C, 40.11; H, 7.77; N, 8.91; Found: C, 40.03; H, 7.86; N, 8.65.

EXAMPLE 10 N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-norvalyl-methionine

The title compound was prepared from the precursor to Example 9 after hydrolysis and deprotection according to the methods of Example 6 and isolated as its trifluoroacetate salt. ¹ H NMR (CD₃ OD) δ 4.57-4.66 (m, 1H), 3.80 (t, 1H, J=8 Hz), 3.04-3.5 (m, 7H), 2.8-2.97 (m, 4H), 2.90 (s, 3H), 2.47-2.7 (m, 2H), 2.13-2.3 (m, 1H), 2.09 (s, 3H), 1.8-2.0 (m, 2H), 1.34-1.6 (m, 2H), 1.2-1.32 (m, 1H), 0.88-1.1 (m, 9H).

Anal. calculated for C₂₀ H₄₂ N₄ O₃ S₂.3CF₃ CO₂ H.H₂ O: C, 38.51; H, 5.84; N, 6.91; Found: C, 38.51; H, 5.71; N, 7.23.

EXAMPLE 11 N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-D-norvalyl-homoserine lactone and N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-D-norvalyl-homoserine

The title compounds were prepared according to the methods of Example 1, substituting D-norvaline methyl ester for isoleucyl benzyl ester, and isolated as its trifluoroacetate salt. ¹ H NMR (CD₃ OD) δ 4.49 (t, 1H, J=9 Hz), 4.28-4.3 (m, 1H), 3.74-3.8 (m, 1H), 3.45-3.5 (m, 1H), 2.8-3.15 (m, 8H), 2.86 (s, 3H), 3.55-2.63 (m, 1H), 2.26-2.73 (m, 1H), 1.75-1.95 (m, 3H), 1.18-1.54 (m, 5H), 0.88-1.02 (m, 9H).

Anal. calculated for C₁₉ H₃₈ N₄ O₃ S.3CF₃ CO₂ H.0.75H₂ O: C, 39.60; H, 5.65; N, 7.39; Found: C, 39.62; H, 6.03; N, 7.23.

The hydroxy acid was generated in situ according to Example 1, Step J.

EXAMPLE 12 3(S)-{N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucylamino}-6,6-dimethyltetrahydropyran-2-one and 2(S)-{N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucylamino}-5-methyl-5-hydroxyhexanoic acid

Step A: 2-N-(t-Butoxycarbonyl)amino-5-hydroxy-5-methylhexanoic acid

To a soln of N-(t-butoxycarbonyl)glutamic acid -5-methyl ester (2.52 g, 0.0096 mol) in THF (32 mL) was added methyl lithium (1.4M in ether) (30.2 mL, 0.042 mol) under argon with stirring at a rate to maintain the reaction temperature at <-60° C. After the addition the mixture was stirred at -70° C. for 1 h, then added to 10% citric acid soln (30 mL) and extracted with EtOAc (3×30 mL). The EtOAc layers were combined, washed with brine, and dried (Na₂ SO₄). Filtration and concentration, followed by chromatography (SiO₂, CHCl₃ : MeOH: HOAc, 90:9:1) gave 1.2 g (48%) of the title compound as a yellow oil which solidified on standing. ¹ H NMR (CDCl₃) δ 55.28 (br s, 1H), 4.35-4.43 (m, 1H), 1.75-2.0 (m, 2H), 1.58 (t, 2H, 9 Hz), 1.46 (s, 9H), 1.24 (s, 6H).

Step B: 3(S)-(t-Butoxycarbonyl)amino-6,6-dimethyltetrahydropyran-2-one

2-N-(t-Butoxycarbonyl)amino-5-hydroxy-5-methylhexanoic acid (1.06 g, 4.05 mmol), dicyclohexylcarbodiimide (DCC) (1.01 g, 4.86 mmol), and 4-dimethylaminopyridine (DMAP) (0.05 g, 0.4 mmol) were dissolved in CH₂ Cl₂ (40 mL) with stirring at ambient temperature under argon. After 0.5 h the reaction mixture was filtered to remove dicylcohexylurea, the filtrate concentrated, then partitioned between EtOAc (100 mL) and 10% citric acid soln (50 mL). The organic layer was separated, washed with H₂ O (3×50 mL), brine (1×50 mL) and dried (Na₂ SO₄). Filtration, concentration, and chromatography (SiO₂, EtOAc: hexane, 1:2) gave 0.6 g (61%) of the title compound as a white solid. ¹ H NMR (CDCl₃) δ 5.33 (br s, 1H), 4.04-4.17 (m, 1H), 2.37-2.48 (m, 1H), 1.8-2.0 (m, 3H), 1.45 (s, 9H), 1.41 (s, 6H).

Step C: 3(S)-Amino-6,6-dimethyl-tetrahydropyran-2-one hydrochloride

3(S)-(t-Butoxycarbonyl)amino-6,6-dimethyltetrahydropyran-2-one (0.36 g, 1.48 mmol) was dissolved in EtOAc (30 mL) and treated with HCl gas at -50° C. for 20 min and stirred at -30° to -50° C. for 20 min. Argon was bubbled into the soln for 10 min, then the soln was concentrated to give 0.265 g (100%) of the title compound as a white solid. ¹ H NMR (CD₃ OD) δ 4.05-4.15 (m, 1H), 2.2-2.32 (m, 1H), 2.0-2.15 (m, 3H), 1.48 (s, 3H), 1.43 (s, 3H).

Step D: 3(S)-{N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucylamino}-3-methyltetrahydropyran-2-one

The title compound was prepared following the methods of Example 1, substituting 3(S)-amino-6,6-dimethyl-tetrahydropyran-2-one hydrochloride for homoserine lactone in Step E. The title compound was obtained as its trifluoroacetate salt. ¹ H NMR (CD₃ OD) δ 4.1-4.2 (m, 1H), 3.55 (d, 2H, J=6 Hz), 3.0-3.3 (m, 6H), 2.90 (t, 2H, 6 Hz), 2.81 (s, 3H), 2.28-2.39 (m, 1H), 1.82-2.15 (m, 5H), 1.55-1.6 (m, 1H), 1.53 (s, 3H), 1.45 (s, 3H), 1.2-1.4 (m, 2H), 0.92-1.04 (m, 12H).

Anal. calculated for C₂₃ H₄₆ N₄ O₃ S.3CF₃ CO₂ H.1.5 H2O: C, 42.07; H, 6.33; N, 6.77; Found: C, 42.20; H, 6.10; N, 7.16.

The hydroxy acid was generated in situ according to Example 1, Step J.

EXAMPLE 13 3(S)-{N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucylamino}-3-methyltetrahydropyran-2-one and 2(S)-{N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucylamino}-2-methyl-5-hydroxypentanoic acid

Step A: 2-Amino-2-methyl-5-hydroxypentanoic acid

Finely ground racemic a-methylglutamic acid (5.0 g, 0.029 mol) was suspended in THF (30 mL), treated with triethylborane (1M in THF, 32.32 mL, 0.032 mol), and heated at reflux for 36 h. After cooling to 0° C. the soln was treated dropwise with borane in THF (1M, 35.26 mL, 0.035 mol) and stirred at 0° C. for 3 h. The mixture was quenched with 5% aq HCl (30 mL), stirred for 0.5 h, concentrated on a rotary evaporator, and the residue dissolved in 5% HCl (44 mL) and heated at reflux for 0.75 h. After cooling and concentrating, the residue was taken up in MeOH (50 mL), concentrated, and this procedure repeated 3×to give 5.69 g of the title compound which was not purified.

Step B: 2-(t-Butyloxycarbonyl)amino-2-methyl-5-hydroxypentanoic acid

2-Amino-2-methyl-5-hydroxypentanoic acid (5.69 g, 0.031 mol) was dissolved in 1,2-dimethoxyethane (DME) (60 mL)- H₂ O (30 mL) with stirring at 0° C. The pH of the soln was adjusted to 9-10 with 1N NaOH soln, then di-t-butyl-dicarbonate (7.45 g, 0.034 mol) in DME (60 mL)- H₂ O (30 mL) was added dropwise while maintaining the mixture at a pH of 9-10 by concomitant addition of 1N NaOH soln. The reaction mixture was stirred at ambient temperature for 48 h with periodic addition of 1N NaOH to maintain the basic pH, then concentrated and partitioned between ether and H₂ O. The aq layer was acidified with 10% citric acid soln, and extracted with EtOAC (3×50 mL). The organic layers were combined, washed with brine, and dried (Na₂ SO₄). Filtration and concentration to dryness gave 3.0 g of crude title compound.

Step C: 3-(t-Butoxycarbonyl)amino-3-methyl-tetrahydropyran-2-one

2-(t-Butyloxycarbonyl)amino-2-methyl-5-hydroxypentanoic acid (3.0 g, 0.012 mol) and EDC (2.56 g, 0.013 mol) were dissolved in DMF (20 mL) and stirred at ambient temperature for 18 h. The reaction mixture was concentrated to dryness, and the residue was partitioned between EtOAc (30 mL)-H₂ O (30 mL), the organic layer separated, washed with brine and dried (Na₂ SO₄). Filtration, concentration, and chromatography (SiO₂, EtOAc: hexane, 1:3) gave 0.86 g (31%) of the title compound. ¹ H NMR (CDCl₃) δ 5.1 (br s, 1H), 4.35-4.55 (m, 2H), 2.49-2.64 (m, 1H), 1.78-2.1 (m, 3H), 1.45 (s, 3H), 1.41 (s, 9H).

Step D: 3-Amino-3-methyl-tetrahydropyran-2-one hydrochloride

The title compound was prepared as described in Example 12, Step C, and the resulting product used without further purification.

Step E: 3(S)-{N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucylamino{-3-methyltetrahydropyran-2-one

The title compound was prepared following the methods of Example 1, substituting 3-amino-3-methyltetrahydropyran-2-one hydrochloride for homoserine lactone in Step E. The title compound was obtained as its trifluoroacetate salt. ¹ H NMR (CD₃ OD) δ 4.42-4.55 (m, 2H), 3.48-3.6 (m, 2H), 3.17-3.28 (m, 1H), 2.88-3.15 (m, 5H), 2.79 (s, 3H), 2.3-2.45 (m, 1H), 1.97-2.18 (m, 2H), 1.82-11.98 (m, 3H), 1.6-1.73 (m, 1H), 1.56 (s, 3H), 1.21-1.5 (m, 4H), 0.86-1.05 (m, 12H).

Anal. calculated for C₂₂ H₄₄ N₄ O₃ S.3CF₃ CO₂ H: C, 42.75; H, 6.02; N, 7.12; Found: C, 42.79; H, 6.18; N, 7.19.

The hydroxy acid was generated in situ according to Example 1, Step J.

EXAMPLE 14 In vitro inhibition of ras farnesyl transferase

Farnesyl-protein transferase (FTase) from bovine brain was chromatographed on DEAE-Sephacel (Pharmacia, 0-0.8M NaCl gradient elution), N-octyl agarose (Sigma, 0-0.6M NaCl gradient elution), and a mono Q HPLC column (Pharmacia, 0-0.3M NaCl gradient). Ras-CVLS at 3.5 μM, 0.25 μM [³ H]FPP, and the indicated compounds were incubated with either a partially purified bovine enzyme preparation or a recombinant human enzyme preparation. The FTase data presented below in Table 1 reflects the ability of the test compound to inhibit RAS farnesylation in vitro, as described in Pompliano, et al., Biochemistry 31, 3800 (1992).

                  TABLE 1                                                          ______________________________________                                         Inhibition of RAS farnesylation by compounds of this invention*                Compound                IC.sub.50 (nM)                                         ______________________________________                                         N-[2(S)-2(R)-amino-3-mercaptopropyl-                                                                   72                                                     amino)-3(S)-methylpentyl]-N-methyl-                                                                    (Bovine)                                               isoleucyl-homoserine                                                           N-[2(S)-2(R)-amino-3-mercaptopropyl-                                                                   20                                                     amino)-3(S)-methylpentyl]-N-methyl-                                                                    (Recombinant                                           isoleucyl-methionine    Human)                                                 ______________________________________                                          *(IC.sub.50  is the concentration of the tet compound which gives 50%          inhibition of FTase under the described assay conditions)                

EXAMPLE 15 In vivo ras farnesylation assay

The cell line used in this assay was the v-ras line, which expressed viral Ha-ras p21. The assay was performed essentially as described in DeClue, J. E. et. al., Cancer Research 51, 712-717, (1991). Cells in 10 cm dishes at 50-75% confluency were treated with the test compound (final concentration of solvent, methanol or dimethyl sulfoxide, was 0.1%). After 4 hours at 37° C., the cells were labelled in 3 ml methionine-free DMEM supplemented with 10% regular DMEM, 2% fetal bovine serum and 400 μCi[³⁵ S]methionine (1000 Ci/mmol). After an additional 20 hours, the cells were lysed in 1 ml lysis buffer (1% NP40/20 mM HEPES, pH 7.5/5 mM MgCl₂ /1 mM DTT/10 μg/ml aprotinen/2 μg/ml leupeptin/2 μg/ml antipain/0.5 mM PMSF) and the lysates cleared by centrifugation at 100,000×g for 45 min. Aliqouts of lysates containing equal numbers of acid-precipitable counts were bought to 1 ml with IP buffer (lysis buffer lacking DTT) and immunoprecipitated with the ras-specific monoclonal antibody Y13-259 (Furth, M. E. et. al., J. Virol. 43, 294-304, (1982)). Following a 2 hour antibody incubation at 4° C., 200 μl of a 25% suspension of protein A-Sepharose coated with rabbit anti rat IgG was added for 45 min. The immunoprecipitates were washed four times with IP was buffer (20 nM HEPES, pH 7.5/1 mM EDTA/ 1% Triton X-100.0.5% deoxycholate/0.1%/SDS/0.1 M NaCl) boiled in SDS-PAGE sample buffer and loaded on 13% acrylamide gels. When the dye front reached the bottom, the gel was fixed, soaked in Enlightening, dried and autoradiographed. The intensities of the bands corresponding to farnesylated and nonfarnesylated ras proteins were compared to determine the percent inhibition of farnesyl transfer to protein. Data for representative test compounds are tabulated in Table 2.

                  TABLE 2                                                          ______________________________________                                         Inhibition of Ras Farnesylation by the compounds of                            this invention in the v-ras cell line                                          Compound               IC.sub.50  (μM)                                      ______________________________________                                         N-[2(S)-2(R)-amino-3-mercaptopropyl-                                                                  50                                                      amino)-3(S)-methylpentyl]-N-methyl-                                            isoleucyl-homoserine lactone                                                   N-[2(S)-2(R)-amino-3-mercaptopropyl-                                                                   5                                                      amino)-3(S)-methylpentyl]-N-methyl-                                            isoleucyl-methionine methyl ester                                              ______________________________________                                     

What is claimed is:
 1. A prodrug of the formula IV: ##STR13## R¹ is hydrogen, an alkyl group, an aralkyl group, an acyl group, an aracyl group, an aroyl group, an alkylsulfonyl group, aralkylsulfonyl group or arylsulfonyl group, wherein alkyl and acyl groups comprise straight chain or branched chain hydrocarbons of 1 to 6 carbon atoms;R² and R³ are the side chains of naturally occurring amino acids, and their oxidized forms which may be methionine sulfoxide or methionine sulfone, or in the alternative may be substituted or unsubstituted aliphatic, aromatic or heteroaromatic groups, comprising allyl, cyclohexyl, phenyl, pyridyl, imidazolyl or saturated chains of 2 to 8 carbon atoms which may be branched or unbranched, wherein the aliphatic substitutents may be substituted with an aromatic or heteroaromatic ring; R⁵ is an alkyl group, wherein the alkyl group comprises straight chain or branched chain hydrocarbons of 1 to 6 carbon atoms, which may be substituted with an aromatic or heteroaromatic group; n is 0, 1 or 2;and the pharmaceutically acceptable salts and disulfides thereof.
 2. The compound which is: N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucyl-homoserine lactone ##STR14##
 3. A prodrug of a compound which inhibits farnesyl-protein transferase which is:N-{2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl}-N-methyl-phenylalanyl-homoserine lactone, N-{2(S)-(2(R)-amino-3-mercaptopropylamino)-3-methyl-butyl}-N-methyl-phenylalanyl-homoserine lactone, 3(S)-{N-{2(S)-(2(R)-amino-3-mercaptopropylamino)-3(s)-methylpentyl}-N-methyl-isoleucylamino}-3-methyltetrahydropyran-2-one, N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3-(S)-methylpentyl]-N-methyl-norvalyl-homoserine lactone, 3(S)-{N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-isoleucylamino}-6,6-dimethyltetrahydropyran-2-one, N-[2(S)-(2(R)-amino-3-mercaptopropylamino)-3(S)-methylpentyl]-N-methyl-D-norvalyl-homoserine lactone,and the pharmaceutically salts and disulfides thereof.
 4. A pharmaceutical composition comprising a pharmaceutical carrier, and dispersed therein a therapeutically effective amount of a compound of claim
 1. 